Electrochemical Co-Production of a Glycol and an Alkene Employing Recycled Halide

ABSTRACT

The present disclosure is a method and system for electrochemically co-producing a first product and a second product. The system may include a first electrochemical cell, a first reactor, a second electrochemical cell, at least one second reactor, and at least one third reactor. The method and system for for co-producing a first product and a second product may include co-producing a glycol and an alkene employing a recycled halide.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application and claims thebenefit under 35 U.S.C. §120 to U.S. patent application Ser. No.13/724,768 filed Dec. 21, 2012, pending. Said U.S. patent applicationSer. No. 13/724,768 filed Dec. 21, 2012 is incorporated by reference inits entirety.

U.S. patent application Ser. No. 13/724,768 filed Dec. 21, 2012 claimsthe benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser.No. 61/720,670 filed Oct. 31, 2012, U.S. Provisional Application Ser.No. 61/703,187 filed Sep. 19, 2012 and U.S. Provisional Application Ser.No. 61/675,938 filed Jul. 26, 2012. Said U.S. Provisional ApplicationSer. No. 61/720,670 filed Oct. 31, 2012, U.S. Provisional ApplicationSer. No. 61/703,187 filed Sep. 19, 2012 and U.S. Provisional ApplicationSer. No. 61/675,938 filed Jul. 26, 2012 are incorporated by reference intheir entireties.

U.S. patent application Ser. No. 13/724,768 filed Dec. 21, 2012 alsoclaims the benefit under 35 U.S.C. §119(e) of U.S. ProvisionalApplication Ser. No. 61/703,229 filed Sep. 19, 2012, U.S. ProvisionalApplication Ser. No. 61/703,158 filed Sep. 19, 2012, U.S. ProvisionalApplication Ser. No. 61/703,175 filed Sep. 19, 2012, U.S. ProvisionalApplication Ser. No. 61/703,231 filed Sep. 19, 2012, U.S. ProvisionalApplication Ser. No. 61/703,232 filed Sep. 19, 2012, United StatesProvisional Application Ser. No. 61/703,234 filed Sep. 19, 2012, U.S.Provisional Application Ser. No. 61/703,238 filed Sep. 19, 2012. TheU.S. Provisional Application Ser. No. 61/703,229 filed Sep. 19, 2012,U.S. Provisional Application Ser. No. 61/703,158 filed Sep. 19, 2012,U.S. Provisional Application Ser. No. 61/703,175 filed Sep. 19, 2012,U.S. Provisional Application Ser. No. 61/703,231 filed Sep. 19, 2012,U.S. Provisional Application Ser. No. 61/703,232 filed Sep. 19, 2012,U.S. Provisional Application Ser. No. 61/703,234 filed Sep. 19, 2012 andU.S. Provisional Application Ser. No. 61/703,238 filed Sep. 19, 2012 arehereby incorporated by reference in their entireties.

The present application incorporates by reference co-pending U.S. patentapplication Ser. No. 13/724,339, filed Dec. 21, 2012, U.S. patentapplication Ser. No. 13/724,878, filed Dec. 21, 2012, U.S. patentapplication Ser. No. 13/724,647, filed Dec. 21, 2012, U.S. patentapplication Ser. No. 13/724,231, filed Dec. 21, 2012, U.S. patentapplication Ser. No. 13/724,807, filed Dec. 21, 2012, U.S. patentapplication Ser. No. 13/724,996, filed Dec. 21, 2012, U.S. patentapplication Ser. No. 13/724,719, filed Dec. 21, 2012, and U.S. patentapplication Ser. No. 13/724,082, filed Dec. 21, 2012 in theirentireties.

TECHNICAL FIELD

The present disclosure generally relates to the field of electrochemicalreactions, and more particularly to methods and/or systems forelectrochemical co-production of a glycol and an alkene employing arecycled reactant.

BACKGROUND

The combustion of fossil fuels in activities such as electricitygeneration, transportation, and manufacturing produces billions of tonsof carbon dioxide annually. Research since the 1970s indicatesincreasing concentrations of carbon dioxide in the atmosphere may beresponsible for altering the Earth's climate, changing the pH of theocean and other potentially damaging effects. Countries around theworld, including the United States, are seeking ways to mitigateemissions of carbon dioxide.

A mechanism for mitigating emissions is to convert carbon dioxide intoeconomically valuable materials such as fuels and industrial chemicals.If the carbon dioxide is converted using energy from renewable sources,both mitigation of carbon dioxide emissions and conversion of renewableenergy into a chemical form that can be stored for later use will bepossible.

SUMMARY OF THE PREFERRED EMBODIMENTS

The present disclosure includes a system and method forelectrochemically co-producing a first product and a second product. Thesystem may include a first electrochemical cell, a first reactor, asecond electrochemical cell, at least one second reactor, and at leastone third reactor. The method and system for co-producing a firstproduct and a second product may include co-producing a glycol and analkene employing a recycled halide.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not necessarily restrictive of the present disclosure. Theaccompanying drawings, which are incorporated in and constitute a partof the specification, illustrate subject matter of the disclosure.Together, the descriptions and the drawings serve to explain theprinciples of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the present disclosure may be betterunderstood by those skilled in the art by reference to the accompanyingfigures in which:

FIG. 1 is a block diagram of a system in accordance with an embodimentof the present disclosure;

FIG. 2 is a block diagram of a system in accordance with anotherembodiment of the present disclosure;

FIG. 3 is a block diagram of a system in accordance with an additionalembodiment of the present disclosure; and

FIG. 4 is a block diagram of a system in accordance with anotheradditional embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the subject matter disclosed,which is illustrated in the accompanying drawings.

The present disclosure includes a system and method forelectrochemically co-producing a first product and a second product. Thesystem may include a first electrochemical cell, a first reactor, asecond electrochemical cell, at least one second reactor, and at leastone third reactor. The method and system for co-producing a firstproduct and a second product may include co-producing a glycol and analkene employing a recycled halide. In one embodiment, the system mayco-produce monoethylene glycol (MEG) and ethylene. An overall equationfor the desired reaction is:

2CO₂+5C₂H₆

C₂H₄(OH)₂+5C₂H₄+2H₂O.

In an advantageous aspect of the present disclosure, chemicals may beco-produced at both the anode and the cathode of each electrochemicalcell. The cathode may be used to reduce carbon dioxide tocarbon-containing chemicals. The anode may be used to make an oxidationproduct for subsequent employment in producing another carbon compound.By co-producing chemicals, the overall energy requirement for makingeach chemical may be reduced by 50% or more. In addition, the cell maybe capable of simultaneously making two or more products with highselectivity. In another advantageous aspect of the present disclosure,carbon dioxide may act to oxidize organic compounds, and the organiccompounds may act to reduce carbon dioxide. The organic compound, suchas ethane, may be the sole source of hydrogen used in the reduction ofcarbon dioxide. Halogens utilized to couple the oxidation of organics tothe reduction of carbon dioxide may be recycled in the process.

Before any embodiments of the disclosure are explained in detail, it isto be understood that the embodiments may not be limited in applicationper the details of the structure or the function as set forth in thefollowing descriptions or illustrated in the figures. Differentembodiments may be capable of being practiced or carried out in variousways. Also, it is to be understood that the phraseology and terminologyused herein is for the purpose of description and should not be regardedas limiting. The use of terms such as “including,” “comprising,” or“having” and variations thereof herein are generally meant to encompassthe item listed thereafter and equivalents thereof as well as additionalitems. Further, unless otherwise noted, technical terms may be usedaccording to conventional usage. It is further contemplated that likereference numbers may describe similar components and the equivalentsthereof.

Referring to FIG. 1, a block diagram of a system 100 in accordance withan embodiment of the present disclosure is shown. System (or apparatus)100 may generally include electrochemical cells, such as a firstelectrochemical cell 102A and a second electrochemical cell 102B, whichmay also be referred as a container, electrolyzer, or cell.Electrochemical cells 102A and 102B may be implemented as a dividedcells. The divided cells may be divided electrochemical cells and/or adivided photo-electrochemical cells. Electrochemical cells 102A and 102Bmay include a first region 116 and a second region 118. First region 116and second region 118 may refer to a compartment, section, or generallyenclosed space, and the like without departing from the scope and intentof the present disclosure. First region 116 may include a cathode 122.Second region 118 may include an anode 124. First region 116 may includea catholyte whereby carbon dioxide from carbon dioxide source 106 isincluded in the catholyte. Second region 118 may include an anolytewhich may include an MX 128 where M is at least one cation and X isselected from a group consisting of F, Cl, Br, I and mixtures thereof.An energy source 114 may generate an electrical potential between theanode 124 and the cathode 122. The electrical potential may be a DCvoltage. Energy source 114 may be configured to supply a variablevoltage or constant current to electrochemical cell 102. Separator 120may selectively control a flow of ions between the first region 116 andthe second region 118. Separator 120 may include an ion conductingmembrane or diaphragm material.

A cation, as used above, refers to a positively charged speciesincluding ions such as Li, Na, K, Cs, Be, Mg, Ca, hydrogen ions,tetraalkyl ammonium ions such as tetrabutylammonium, tetraethylammonium,and tetraalkylphosphonium ions such as tetrabutylphosphonium,tetraethylphosphonium, and in general, R₁R₂R₃R₄N or R₁R₂R₃R₄P where R₁to R₄ are independently alkyl, cycloalkyl, branched alkyl, and aryl.

First electrochemical cell 102A is generally operational to reducecarbon dioxide in the first region 116 to a first product recoverablefrom the first region 116, such as a carboxylate 130 or carboxylate saltwhile producing a halogen 132 recoverable from the second region 118.

Carbon dioxide source 106 may provide carbon dioxide to the first region116 of first electrochemical cell 102A. In some embodiments, the carbondioxide is introduced directly into the region 116 containing thecathode 122. It is contemplated that carbon dioxide source may include asource of a mixture of gases in which carbon dioxide has been filteredor separated from the gas mixture.

In one embodiment, carbon dioxide may be reduced to an oxalate salt atthe cathode 122 of the first electrochemical cell 102A while bromine isproduced at the anode 124. The two feeds for the electrochemical cell102A first region are carbon dioxide and a bromide salt such as LiBr,NaBr, KBr, MgBr₂, alkylammonium bromide, tetraalkylammonium salts suchas tetramethylammonium bromide, tetraethylammonium bromide,tetrabutylammonium bromide, choline bromide, benzyltrimethylammoniumbromide, and butyltrimethylammonium bromide. Oxalate salt produced atcathode 122 of the first electrochemical cell 102A may betetrabutylammonium oxalate. However, other organic salts may be producedto include formates, glyoxylates, glycolates, and acetates, depending onthe solvent utilized. While any solvent or any mix of solvents may beused, aprotic solvents such as propylene carbonate may be preferred. Aseparator 120 may be utilized to minimize or prevent oxidation of thefirst region 116 product and to minimize or prevent mixing of the anode124 and cathode 122 products. Separator 120 may be a cation exchangemembrane, such as Nafion, or a micro or nanoporous diaphram.Electrochemical cell 102A may be operated in a temperature range from 0°C. to 150° C. Temperatures above 60° C. are preferred for production ofgas phase Br₂. Electrochemical cell 102A may be operated in a pressurerange from 1 to 200 atmospheres, with 1 to 10 atmospheres preferred.

It is contemplated that each electrochemical cell, 102A and 102B, mayinclude a first product extractor 110 and second product extractor 113.Product extractors 110, 113 may implement an organic product and/orinorganic product extractor. First product extractor 110 is generallyoperational to extract (separate) a product from the first region 116.Second product extractor 113 may extract the second product from thesecond region 118. It is contemplated that first product extractorand/or second product extractor may be implemented with electrochemicalcells 102A and 102B, or may be remotely located from the electrochemicalcells 102A 102B. Additionally, it is contemplated that first productextractor and/or second product extractor may be implemented in avariety of mechanisms and to provide desired separation methods, such asfractional distillation, without departing from the scope and intent ofthe present disclosure. It is further contemplated that extractedproduct may be presented through a port of the system 100 for subsequentstorage and/or consumption by other devices and/or processes.

An anode side of the reaction occurring in the second region 118 offirst electrochemical cell 102A may include a recycled reactant of MX.Recycled reactant may include an halide salt which may be a byproduct ofa reaction of first reactor 134. For example, the recycled reactant mayinclude MX where where M is at least one alkali metal and X is selectedfrom a group consisting of F, Cl, Br, I and mixtures thereof. M mayinclude H, Li, Na, K, Cs, Mg, Ca, or other metal, or R₁R₂R₃R₄P⁺,R₁R₂R₃R₄N⁺—where each R is independently alkyl, branched alkyl,cycloalkyl, or aryl—or a cation; and X is F, Cl, Br, I, or an anion; andmixtures thereof. The anode side of the reaction may produce a halogen132 which may be presented to second reactor 138A.

System 100 may include second reactor 138A which may receive halogen 132produced by the second region 118 of first electrochemical cell 102A.Second reactor 138A may react halogen 132 with an alkane or aromaticcompound or other carbon compounds that can be partially oxidized with ahalogen or mixtures thereof 140 to produce a halogenated compound 144and HX 148. HX 148 may be another recycled reactant which may berecycled back to the second region 118 as an input feed to the secondregion 118 of second electrochemical cell 102B and as an input of firstreactor 134.

In one embodiment, the alkane 140 may be ethane and second reactor 138Amay produce bromoethane. While selectivity for 1-bromoethane isgenerally greater than 85%, some dibromoethane may also be produced. Thedibromoethane may be sold as a separate product, converted to asecondary product such as acetylene, recycled back to the secondaryreactor 138A in order to improve selectivity for 1-bromoethane, and/orcatalytically converted into 1-bromoethane. HBr will be co-produced withbromoethane and may be recycled back to first reactor 134 or the secondregion 118 of electrochemical cell 102B. In another embodiment, thearomatic compound may be ethylbenzene which may be brominated to makebromoethylbenzene and HBr.

Halogenated compound 144 may be fed to third reactor 152A. Third reactor152A may perform a dehydrohalogenation reaction or another chemicalreaction of halogenated compound 144 to produce a second product 156. Inone embodiment, halogen may refer to Br₂ which may react with ethane toproduce bromoethane. The dehydrohalogenation reaction of bromoethane mayproduce ethylene and HBr. The dehydrohalogenation reaction ofdibromoethane or dichloroethane may produce acetylene. Thedehydrohalogenation of bromopropane may produce propylene. Thedehydrohalogenation of bromobutane may produce 1-butene, 2-butene,butadiene, or a mix thereof. The dehydrohalogenation of bromoisobutaneor iodoisobutane may produce isobutylene. The dehydrohalogenationreaction of bromoethylbenzene may produce styrene.

First reactor 134 may receive an input feed of carboxylate 130 orcarboxylate salt along with recycled input feed of HX 148 to producecarboxylic acid 160. Second electrochemical cell 102B may receivecarboxylic acid 160 as a catholyte feed to the first region 116 of thesecond electrochemical cell 102B. An anode side of the reactionoccurring in the second region 118 of second electrochemical cell 102Bmay include a recycled reactant of HX 149. Recycled reactant may includea hydrogen halide and may include byproducts of at least one secondreactor 138A, 138B, and third reactor 152A, 152B.

A cathode reaction of the first region 116 may produce a first product164 recoverable from the first region 116 of the second electrochemicalcell 102B after extractor 110. First product may include at least one ofanother carboxylic acid, an aldehyde, a ketone, a glycol, or an alcohol.Additional examples of first product 164 may include glyoxylic acid,glyoxal, glycolic acid, glycolaldehyde, acetic acid, acetaldehyde,ethanol, ethane, ethylene or ethylene glycol. An anode reaction of thesecond region 118 of the second electrochemical cell 102B may produce ahalogen 132. Halogen may include Br₂ and may be fed to second reactor138B.

In one embodiment, oxalic acid may be produced by first reactor 134 andfirst region 116 of second electrochemical cell 102B may reduce theoxalic acid to monoethylene glycol while HBr is oxidized to Br₂ in thesecond region 118. Catholyte of first region 116 may preferably utilizewater as solvent, but may include a non-aqueous solvent or mix ofsolvents. The electrolyte in the cathode compartment is preferably anacid such as HBr, HCl, HI, HF, or H₂SO₄, but may include any mixture ofsalts or acids. The catholyte pH may be less than 7 and preferablybetween 1 and 5. A homogenous heterocyclic catalyst may be employed inthe catholyte. The anolyte may be solely anhydrous gas-phase HBr or HClor may include a liquid solvent, such as water, in which HBr or HCl isdissolved. In the case of a liquid anolyte, the HBr anolyteconcentration may be in the range of 5 wt % to 50 wt %, more preferablyin the range of 10 wt % to 40 wt %, and more preferably in the 15 wt %to 30 wt % range, with a corresponding 2 to 30 wt % bromine content asHBr₃ in the solution phase. The HBr content in the anolyte solution maycontrol the anolyte solution conductivity, and thus the anolyte regionIR voltage drop. If the anode is run with gas phase HBr, then HBrconcentrations may approach 100% by wt % and may be run in anhydrousconditions. The cell temperature may range from 10° C. to 100° C., buttemperatures less than 60° C. are preferred to produce Br₂ in the liquidphase.

Second reactor 138B may react halogen 132 with a carbon compound 140, asdescribed above, to produce a halogenated compound 144 and HX 149. HX149 may be another recycled reactant which may be recycled back to thesecond region 118 as an input feed to the second region 118 of secondelectrochemical cell 102B and as an input of first reactor 134.Halogenated compound 144 may be fed to third reactor 152B.

Third reactor 152A may perform a dehydrohalogenation reaction or anotherchemical reaction of halogenated compound 144 to produce a secondproduct 157. Second product 157 may include an alkene, alkyne, alcohol,aldehyde, ketone, or longer-chain alkane. It is contemplated that thereaction may occur at elevated temperatures and may include the use of ametal or metal oxide catalyst to reduce the thermal energy required.Temperature ranges for the reaction are from 25° C. to 1,000° C., withtemperatures below 500° C. preferable.

In one embodiment, halogen may refer to Br₂ which may react with ethaneto produce bromoethane. The dehydrohalogenation reaction of bromoethanemay produce ethylene and HBr. It is contemplated that a diverter, ordiverter valve may be inserted in the feed for the HX 148 feed betweenthe second reactor 138A, 138B and the third reactors 152A and 152B andan input of the first reactor 134 and the input to the second region 118of the second electrochemical cell 102B to ensure a proper amount of HXis supplied to each of the first reactor 134 and the input to the secondregion 118 of the second electrochemical cell 102B.

Referring to FIG. 2, a block diagram of a system 200 in accordance withanother embodiment of the present disclosure is shown. System 200 may besubstantially similar to system 100 of FIG. 1. However, system 200 mayinclude a second reactor 138 implemented as a single reactor and thirdreactor 152 implemented as a single reactor, rather than as two or morereactors as shown in system 100 of FIG. 1. It is contemplated thatsystem 200 may also include a diverter, or diverter valve inserted inthe feed for the HX 148 feed between the second reactor 138 and thethird reactor 152 and an input of the first reactor 134 and the input tothe second region 118 of the second electrochemical cell 102B to ensurea proper amount of HX is supplied to each of the first reactor 134 andthe input to the second region 118 of the second electrochemical cell102B. Second product 157 from third reactor 152 may include an alkene,alkyne, alcohol, aldehyde, ketone, or longer-chain alkane.

Referring to FIG. 3, a block diagram of a system 300 in accordance withan additional embodiment of the present disclosure is shown. System 300may include a single electrochemical cell 102. Carbon dioxide source 106may provide carbon dioxide to the first region 116 of firstelectrochemical cell 102. Cathode reaction may reduce carbon dioxide toa carbon dioxide reduction product such as CO 310. An anode side of thereaction occurring in the second region 118 of first electrochemicalcell 102 may include a recycled reactant of HX where H is hydrogen and Xis selected from a group consisting of F, Cl, Br, I and mixturesthereof. The anode side of the reaction may produce a halogen 132 whichmay be provided to first reactor 138.

First reactor 138 may react halogen 132, such as Br₂ with a compound140, as described above, such as ethane, to produce a halogenatedcompound 144, such as bromoethane and HX 148, such as HBr. HX 148 may berecycled reactant which may be recycled back to the second region 118 ofelectrochemical cell 102. Halogenated compound 144 may be fed to secondreactor 152 to produce a second product 156. Second product 156 mayinclude an alkene, alkyne, alcohol, aldehyde, ketone, or longer-chainalkane, such as ethylene.

CO 310 may be fed to third reactor 312. Third reactor 312 may perform awater gas shift reaction and react CO 310 and water 316 to producecarbon dioxide 320 and H₂ 324. Carbon dioxide 320 may be recycled backto the input of the first region 116 of electrochemical cell 102. H₂ 324may be fed to fourth reactor 344. Fifth reactor 328 may receive CO 310from the first region 116 of electrochemical cell 102 and may receive anO₂ 332 input and a methanol input 336 supplied by a methanol source 334to produce an intermediate product 340. In one embodiment, intermediateproduct 340 may be dimethyl oxalate. The intermediate product 340, suchas dimethyl oxalate, may be fed to fourth reactor 344. Fourth reactor344 may react intermediate product 340 with H₂ 324 reduce theintermediate product 340 to produce a first product 164 and a methanol336 byproduct which is recycled back to reactor 328. First product 164may include an glyoxylic acid, glyoxal, glycolic acid, glycolaldehyde,acetic acid, acetaldehyde, ethanol, ethane, ethylene, or ethyleneglycol.

Referring to FIG. 4, a block diagram of a system 400 in accordance withanother additional embodiment of the present disclosure is shown. System400 may include a single electrochemical cell 102. A water source 406,which may include HX where H is hydrogen and X is selected from a groupconsisting of F, Cl, Br, I and mixtures thereof, may be provided to thefirst region 116 of electrochemical cell 102. Water with HX 406 may beproduced at the first region 116 and recycled back to an input of thefirst region 116. Cathode reaction may also produce H₂ 410. An anodeside of the reaction occurring in the second region 118 of firstelectrochemical cell 102 may include a recycled reactant of HX 148. Theanode side of the reaction may produce a halogen 132 which may beprovided to first reactor 138.

First reactor 138 may react halogen 132, such as Br₂ with a compound140, as described above, such as ethane, to produce a halogenatedcompound 144, such as bromoethane and HX 148, such as HBr. HX 148 may bea recycled reactant which may be recycled back to the second region 118of electrochemical cell 102. Halogenated compound 144 may be fed tosecond reactor 152 to produce a second product 156. Second product 156may include an alkene, alkyne, alcohol, aldehyde, ketone, orlonger-chain alkane, such as ethylene.

H₂ 410 may be fed to third reactor 412. Reactor 412 may perform areverse water gas shift reaction and react H₂ 410 and carbon dioxide 316to produce water 420 and CO 424. Water may be recycled to an input ofthe first region 116 of electrochemical cell. CO 424 may be fed tofourth reactor 428. Fourth reactor 428 may react CO 424 with O₂ 432 andmethanol 436 supplied from methanol source 434 to produce anintermediate product 440. Intermediate product 440 may be dimethyloxalate. The intermediate product 440, such as dimethyl oxalate, may befed to fifth reactor 444. Reactor 444 may react intermediate product 440with H₂ 410 from second region 116 of electrochemical cell 102 to reducethe intermediate product to produce a first product 164 and a methanol336 byproduct which is recycled back to fourth reactor 428. Firstproduct 164 may include an glyoxylic acid, glyoxal, glycolic acid,glycolaldehyde, acetic acid, acetaldehyde, ethanol, ethane, ethylene, orethylene glycol.

In addition to the systems 300, 400 of FIG. 3 and FIG. 4, another systemto produce ethylene glycol may include producing oxalate in a firstelectrochemical cell from carbon dioxide and Br₂ from MBr, where M is acation. A second electrochemical cell may utilize HBr at the anode. Thesecond electrochemical cell may produce H₂ at the cathode and Br₂ at theanode. Br₂ may be used in the thermal processes to make HBr, which maybe recycled to the HBr electrochemical cell and also used to acidifyoxalate to oxalic acid. The oxalic acid may be reduced to ethyleneglycol in a thermal process utilizing H₂ from the HBr electrolyzer.Oxalic acid may also be reduced to glyoxylic acid, glycolic acid,glyoxal, glycolaldehyde, acetic acid, acetaldehyde, and/or ethanol.

It is contemplated that a receiving feed may include various mechanismsfor receiving a supply of a product, whether in a continuous, nearcontinuous or batch portions.

It is further contemplated that the structure and operation of theelectrochemical cell 102, which includes electrochemical cells 102A and102B, and 102 in FIGS. 1-4, may be adjusted to provide desired results.For example, the electrochemical cell 102 may operate at higherpressures, such as pressure above atmospheric pressure which mayincrease current efficiency and allow operation of the electrochemicalcell at higher current densities.

Additionally, the cathode 122 and anode 124 may include a high surfacearea electrode structure with a void volume which may range from 30% to98%. The electrode void volume percentage may refer to the percentage ofempty space that the electrode is not occupying in the total volumespace of the electrode. The advantage in using a high void volumeelectrode is that the structure has a lower pressure drop for liquidflow through the structure. The specific surface area of the electrodebase structure may be from 2 cm²/cm³ to 500 cm²/cm³ or higher. Theelectrode specific surface area is a ratio of the base electrodestructure surface area divided by the total physical volume of theentire electrode. It is contemplated that surface areas also may bedefined as a total area of the electrode base substrate in comparison tothe projected geometric area of the current distributor/conductor backplate, with a preferred range of 2× to 1000× or more. The actual totalactive surface area of the electrode structure is a function of theproperties of the electrode catalyst deposited on the physical electrodestructure which may be 2 to 1000 times higher in surface area than thephysical electrode base structure.

Cathode 122 may be selected from a number of high surface area materialsto include copper, stainless steels, transition metals and their alloysand oxides, carbon, and silicon, which may be further coated with alayer of material which may be a conductive metal or semiconductor. Thebase structure of cathode 122 may be in the form of fibrous,reticulated, or sintered powder materials made from metals, carbon, orother conductive materials including polymers. The materials may be avery thin plastic screen incorporated against the cathode side of themembrane to prevent the membrane 120 from directly touching the highsurface area cathode structure. The high surface area cathode structuremay be mechanically pressed against a cathode current distributorbackplate, which may be composed of material that has the same surfacecomposition as the high surface area cathode.

In addition, cathode 122 may be a suitable conductive electrode, such asAl, Au, Ag, Bi, C, Cd, Co, Cr, Cu, Cu alloys (e.g., brass and bronze),Ga, Hg, In, Mo, Nb, Ni, NiCo₂O₄, Ni alloys (e.g., Ni 625, NiHX), Ni—Fealloys, Pb, Pd alloys (e.g., PdAg), Pt, Pt alloys (e.g., PtRh), Rh, Sn,Sn alloys (e.g., SnAg, SnPb, SnSb), Ti, V, W, Zn, stainless steel (SS)(e.g., SS 2205, SS 304, SS 316, SS 321), austenitic steel, ferriticsteel, duplex steel, martensitic steel, Nichrome (e.g., NiCr 60:16 (withFe)), elgiloy (e.g., Co—Ni—Cr), degenerately doped p-Si, degeneratelydoped p-Si:As, degenerately doped p-Si:B, degenerately doped n-Si,degenerately doped n-Si:As, and degenerately doped n-Si:B. These metalsand their alloys may also be used as catalytic coatings on the variousmetal substrates. Other conductive electrodes may be implemented to meetthe criteria of a particular application. For photo-electrochemicalreductions, cathode 122 may be a p-type semiconductor electrode, such asp-GaAs, p-GaP, p-InN, p-InP, p-CdTe, p-GalnP₂ and p-Si, or an n-typesemiconductor, such as n-GaAs, n-GaP, n-InN, n-InP, n-CdTe, n-GalnP₂ andn-Si. Other semiconductor electrodes may be implemented to meet thecriteria of a particular application including, but not limited to, CoS,MoS₂, TiB, WS₂, SnS, Ag₂S, CoP₂, Fe₃P, Mn₃P₂, MoP, Ni₂Si, MoSi₂, WSi2,CoSi₂, Ti₄O₇, SnO₂, GaAs, GaSb, Ge, and CdSe.

Catholyte may include a pH range from 1 to 12 when an aqeuous solvent isemployed, preferably from pH 4 to pH 10. The selected operating pH maybe a function of any catalysts utilized in operation of theelectrochemical cell 102. Preferably, catholyte and catalysts may beselected to prevent corrosion at the electrochemical cell 102. Catholytemay include homogeneous catalysts. Homogeneous catalysts are defined asaromatic heterocyclic amines and may include, but are not limited to,unsubstituted and substituted pyridines and imidazoles. Substitutedpyridines and imidazoles may include, but are not limited to mono anddisubstituted pyridines and imidazoles. For example, suitable catalystsmay include straight chain or branched chain lower alkyl (e.g., Cl-C10)mono and disubstituted compounds such as 2-methylpyridine, 4-tertbutylpyridine, 2,6 dimethylpyridine (2,6-lutidine); bipyridines, such as4,4′-bipyridine; amino-substituted pyridines, such as 4-dimethylaminopyridine; and hydroxyl-substituted pyridines (e.g., 4-hydroxy-pyridine)and substituted or unsubstituted quinoline or isoquinolines. Thecatalysts may also suitably include substituted or unsubstituteddinitrogen heterocyclic amines, such as pyrazine, pyridazine andpyrimidine. Other catalysts generally include azoles, imidazoles,indoles, oxazoles, thiazoles, substituted species and complex multi-ringamines such as adenine, pterin, pteridine, benzimidazole, phenonthrolineand the like.

The catholyte may include an electrolyte. Catholyte electrolytes mayinclude alkali metal bicarbonates, carbonates, sulfates, phosphates,borates, and hydroxides. The electrolyte may comprise one or more ofNa₂SO₄, KCl, NaNO₃, NaCl, NaF, NaClO₄, KClO₄, K₂SiO₃, CaCl₂, aguanidinium cation, an H cation, an alkali metal cation, an ammoniumcation, an alkylammonium cation, a tetraalkyl ammonium cation, a halideanion, an alkyl amine, a borate, a carbonate, a guanidinium derivative,a nitrite, a nitrate, a phosphate, a polyphosphate, a perchlorate, asilicate, a sulfate, and a hydroxide. In one embodiment, bromide saltssuch as NaBr or KBr may be preferred.

The catholyte may further include an aqueous or non-aqueous solvent. Anaqueous solvent may include greater than 5% water. A non-aqueous solventmay include as much as 5% water. A solvent may contain one or more ofwater or a non-aqueous solvent. Representative solvents includemethanol, ethanol, acetonitrile, propylene carbonate, ethylenecarbonate, dimethyl carbonate, diethyl carbonate, dimethylsulfoxide,dimethylformamide, acetonitrile, acetone, tetrahydrofuran,N,N-dimethylacetaminde, dimethoxyethane, diethylene glycol dimethylester, butyrolnitrile, 1,2-difluorobenzene, γ-butyrolactone,N-methyl-2-pyrrolidone, sulfolane, 1,4-dioxane, nitrobenzene,nitromethane, acetic anhydride, hexane, heptane, octane, kerosene,toluene, xylene, ionic liquids, and mixtures thereof.

In one embodiment, a catholyte/anolyte flow rate may include acatholyte/anolyte cross sectional area flow rate range such as 2-3,000gpm/ft² or more (0.0076-11.36 m³/m²). A flow velocity range may be 0.002to 20 ft/sec (0.0006 to 6.1 m/sec). Operation of the electrochemicalcell catholyte at a higher operating pressure allows more dissolvedcarbon dioxide to dissolve in the aqueous solution. Typically,electrochemical cells can operate at pressures up to about 20 to 30 psigin multi-cell stack designs, although with modifications, theelectrochemical cells may operate at up to 100 psig. The electrochemicalcell may operate anolyte at the same pressure range to minimize thepressure differential on a separator 120 or membrane separating the tworegions. Special electrochemical designs may be employed to operateelectrochemical units at higher operating pressures up to about 60 to100 atmospheres or greater, which is in the liquid CO₂ and supercriticalCO₂ operating range.

In another embodiment, a portion of a catholyte recycle stream may beseparately pressurized using a flow restriction with backpressure orusing a pump, with CO₂ injection, such that the pressurized stream isthen injected into the catholyte region of the electrochemical cellwhich may increase the amount of dissolved CO₂ in the aqueous solutionto improve the conversion yield. In addition, micro-bubble generation ofcarbon dioxide can be conducted by various means in the catholyterecycle stream to maximize carbon dioxide solubility in the solution.

Catholyte may be operated at a temperature range of −10 to 95° C., morepreferably 5-60° C. The lower temperature will be limited by thecatholytes used and their freezing points. In general, the lower thetemperature, the higher the solubility of CO₂ in an aqueous solutionphase of the catholyte, which would help in obtaining higher conversionand current efficiencies. The drawback is that the operatingelectrochemical cell voltages may be higher, so there is an optimizationthat would be done to produce the chemicals at the lowest operatingcost. In addition, the catholyte may require cooling, so an externalheat exchanger may be employed, flowing a portion, or all, of thecatholyte through the heat exchanger and using cooling water to removethe heat and control the catholyte temperature.

Anolyte operating temperatures may be in the same ranges as the rangesfor the catholyte, and may be in a range of 0° C. to 95° C. In addition,the anolyte may require cooling, so an external heat exchanger may beemployed, flowing a portion, or all, of the anolyte through the heatexchanger and using cooling water to remove the heat and control theanolyte temperature.

Electrochemical cells may include various types of designs. Thesedesigns may include zero gap designs with a finite or zero gap betweenthe electrodes and membrane, flow-by and flow-through designs with arecirculating catholyte electrolyte utilizing various high surface areacathode materials. The electrochemical cell may include floodedco-current and counter-current packed and trickle bed designs with thevarious high surface area cathode materials. Also, bipolar stack celldesigns and high pressure cell designs may also be employed for theelectrochemical cells.

Anode electrodes may be the same as cathode electrodes or different.Anode 124 may include electrocatalytic coatings applied to the surfacesof the base anode structure. Anolytes may be the same as catholytes ordifferent. Anolyte electrolytes may be the same as catholyteelectrolytes or different. Anolyte may comprise solvent. Anolyte solventmay be the same as catholyte solvent or different. For example, for HBr,acid anolytes, and oxidizing water generating oxygen, the preferredelectrocatalytic coatings may include precious metal oxides such asruthenium and iridium oxides, as well as platinum and gold and theircombinations as metals and oxides on valve metal substrates such astitanium, tantalum, zirconium, or niobium. For bromine and iodine anodechemistry, carbon and graphite are particularly suitable for use asanodes. Polymeric bonded carbon material may also be used. For otheranolytes, comprising alkaline or hydroxide electrolytes, anodes mayinclude carbon, cobalt oxides, stainless steels, transition metals, andtheir alloys and combinations. High surface area anode structures thatmay be used which would help promote the reactions at the anodesurfaces. The high surface area anode base material may be in areticulated form composed of fibers, sintered powder, sintered screens,and the like, and may be sintered, welded, or mechanically connected toa current distributor back plate that is commonly used in bipolarelectrochemical cell assemblies. In addition, the high surface areareticulated anode structure may also contain areas where additionalapplied catalysts on and near the electrocatalytic active surfaces ofthe anode surface structure to enhance and promote reactions that mayoccur in the bulk solution away from the anode surface such as thereaction between bromine and the carbon based reactant being introducedinto the anolyte. The anode structure may be gradated, so that thedensity of the may vary in the vertical or horizontal direction to allowthe easier escape of gases from the anode structure. In this gradation,there may be a distribution of particles of materials mixed in the anodestructure that may contain catalysts, such as metal halide or metaloxide catalysts such as iron halides, zinc halides, aluminum halides,cobalt halides, for the reactions between the bromine and thecarbon-based reactant. For other anolytes comprising alkaline, orhydroxide electrolytes, anodes may include carbon, cobalt oxides,stainless steels, and their alloys and combinations.

Separator 120, also referred to as a membrane, between a first region118 and second region 118, may include cation ion exchange typemembranes. Cation ion exchange membranes which have a high rejectionefficiency to anions may be preferred. Examples of such cation ionexchange membranes may include perfluorinated sulfonic acid based ionexchange membranes such as DuPont Nafion® brand unreinforced types N117and N120 series, more preferred PTFE fiber reinforced N324 and N424types, and similar related membranes manufactured by Japanese companiesunder the supplier trade names such as AGC Engineering (Asahi Glass)under their trade name Flemion®. Other multi-layer perfluorinated ionexchange membranes used in the chlor alkali industry may have a bilayerconstruction of a sulfonic acid based membrane layer bonded to acarboxylic acid based membrane layer, which efficiently operates with ananolyte and catholyte above a pH of about 2 or higher. These membranesmay have a higher anion rejection efficiency. These are sold by DuPontunder their Nafion® trademark as the N900 series, such as the N90209,N966, N982, and the 2000 series, such as the N2010, N2020, and N2030 andall of their types and subtypes. Hydrocarbon based membranes, which aremade from of various cation ion exchange materials can also be used ifthe anion rejection is not as desirable, such as those sold by Sybronunder their trade name Ionac®, AGC Engineering (Asahi Glass) under theirSelemion® trade name, and Tokuyama Soda, among others on the market.Ceramic based membranes may also be employed, including those that arecalled under the general name of NASICON (for sodium super-ionicconductors) which are chemically stable over a wide pH range for variouschemicals and selectively transports sodium ions, the composition isNa₁+xZr₂Si_(x)P₃-xO₁₂, and well as other ceramic based conductivemembranes based on titanium oxides, zirconium oxides and yttrium oxides,and beta aluminum oxides. Alternative membranes that may be used arethose with different structural backbones such as polyphosphazene andsulfonated polyphosphazene membranes in addition to crown ether basedmembranes. Preferably, the membrane or separator is chemically resistantto the anolyte and catholyte and operates at temperatures of less than600 degrees C., and more preferably less than 500 degrees C.

A rate of the generation of reactant formed in the anolyte compartmentfrom the anode reaction, such as the oxidation of HBr to bromine, iscontemplated to be proportional to the applied current to theelectrochemical cell 102B. The anolyte product output in this range canbe such that the output stream contains little or no free bromine in theproduct output, or it may contain unreacted bromine. The operation ofthe extractor and its selected separation method, for example fractionaldistillation, the actual products produced, and the selectivity may beadjusted to obtain desired characteristics. Any of the unreactedcomponents would be recycled to the second region 118.

Similarly, a rate of the generation of the formed electrochemical carbondioxide reduction product, such as CO, is contemplated to beproportional to the applied current to electrochemical cells 102, 102A,and 102B. The rate of the input or feed of the carbon dioxide source 106into the first region 116 should be fed in a proportion to the appliedcurrent. The cathode reaction efficiency would determine the maximumtheoretical formation in moles of the carbon dioxide reduction product.It is contemplated that the ratio of carbon dioxide feed to thetheoretical moles of potentially formed carbon dioxide reduction productwould be in a range of 100:1 to 2:1, and preferably in the range of 50:1to 5:1, where the carbon dioxide is in excess of the theoreticalrequired for the cathode reaction. The carbon dioxide excess would thenbe separated and recycled back to the first region 116.

In the present disclosure, the methods disclosed may be implemented assets of instructions or software readable by a device. Further, it isunderstood that the specific order or hierarchy of steps in the methodsdisclosed are examples of exemplary approaches. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the method can be rearranged while remaining within thedisclosed subject matter. The accompanying method claims presentelements of the various steps in a sample order, and are not necessarilymeant to be limited to the specific order or hierarchy presented.

It is believed that the present disclosure and many of its attendantadvantages will be understood by the foregoing description, and it willbe apparent that various changes may be made in the form, constructionand arrangement of the components without departing from the disclosedsubject matter or without sacrificing all of its material advantages.The form described is merely explanatory, and it is the intention of thefollowing claims to encompass and include such changes.

What is claimed is:
 1. A system for co-producing a first product and asecond product, comprising: a first electrochemical cell, the firstelectrochemical cell including a first region, a second region and aseparator that selectively controls a flow of ions between the firstregion and the second region, the first region having a cathode with acatholyte comprising carbon dioxide, the second region having an anodewith an anolyte comprising MX where M is at least one cation and X isselected from a group consisting of F, Cl, Br, I and mixtures thereof,wherein when there is an electric potential applied between the anodeand cathode, M-carboxylate is produced in the first region and a halogenis produced in the second region; a first reactor, the first reactorreacts the M-carboxylate with HX to produce carboxylic acid and MX, theMX being recycled to an input of the second region of the firstelectrochemical cell; a second electrochemical cell, the secondelectrochemical cell including a first region, a second region and aseparator that selectively controls a flow of ions between the firstregion and the second region, the first region having a cathode with acatholyte comprising the carboxylic acid, the second region having ananode with an anolyte comprising HX, wherein when there is an electricpotential applied between the anode and cathode, at least one of anothercarboxylic acid, an aldehyde, a ketone, a glycol or an alcohol isproduced at the first region of the second electrochemical cell and ahalogen is produced in the second region of the second electrochemicalcell; at least one second reactor, the at least one second reactorreacts the halogen from the second region of the first electrochemicalcell and the second region of the second electrochemical cell with analkane, aromatic compound, or other carbon compound to produce ahalogenated compound and HX, the HX being recycled back to the secondregion of the second electrochemical cell and to the input of the firstreactor; and at least one third reactor, the at least one third reactorreacts the halogenated compound to produce at least one of an alkene,alkyne, ketone, alcohol, aldehyde, unsaturated carbon compound, orlonger-chain alkane, and HX, the HX being recycled back to the secondregion of the second electrochemical cell and to the input of the firstreactor.
 2. The system according to claim 1, wherein the halogenincludes at least one of F₂, Cl₂, Br₂ or I₂.
 3. The system according toclaim 1, wherein the alkane, aromatic compound, or other carbon compoundincludes at least one of methane, ethane, propane, or butane.
 4. Thesystem according to claim 1, wherein the M-carboxylate is M oxalate. 5.The system according to claim 1, wherein at least one of glyoxylic acid,glyoxal, glycolic acid, glycolaldehyde, acetic acid, acetaldehyde,ethanol, ethane, ethylene, or ethylene glycol is recoverable from thefirst region of the second electrochemical cell.
 6. The system accordingto claim 2, wherein the cathode and the anode of the firstelectrochemical cell and the cathode and the anode of the secondelectrochemical cell, are separated by an ion permeable barrier thatoperates at a temperature less than 600 degrees C.
 7. The systemaccording to claim 6, wherein the ion permeable barrier includes one ofa polymeric or inorganic ceramic-based ion permeable barrier.
 8. Thesystem according to claim 1, wherein the catholyte of the secondelectrochemical cell is liquid phase and the anolyte is gas phase. 9.The system according to claim 1, wherein at least one of: the catholyteand the anolyte of the first electrochemical cell; and the catholyte andthe anolyte of the second electrochemical cell; are non-aqueous.